Is CVE-2026-54911 actively exploited?

No active exploitation of CVE-2026-54911 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-54911 be exploited remotely?

Yes. CVE-2026-54911 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-54911?

CVE-2026-54911 has a CVSS score of 6.5 (MEDIUM).

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MEDIUM

CVE-2026-54911

CWE-20Published: June 22, 2026· Updated: Jun 26, 2026

6.5

CVSS v3.1

EPSS:0.29%probability of exploitation in 30 daysPercentile:20.2th

Official Description

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.

NVD Source

Technical Analysis

CVE-2026-54911 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.